1. Field of the Invention
The present invention relates to a motor controller for controlling the rotation direction and rotation speed of a motor of a control target such as an electric car operated by a radio control device, and more particularly, to a motor controller for radio control, which includes a changeover unit for changing the manipulation state of a manipulation tool from a braking state to a reverse moving state.
2. Description of the Prior Art
A conventional motor controller is used in a control target such as an electric car operated using a radio control device to control the rotation direction and rotation speed of a motor installed in the control target for forward moving, reverse moving, and/or braking of the control target.
There are various motor controllers, such as a motor controller installed in a model airplane for controlling only the forward moving of the model airplane, and a motor controller installed in an electric car for controlling the forward moving, reverse moving, and/or braking of the electric car.
Among such conventional motor controllers, there is a commercially available motor controller that is configured to be installed in an electric car for controlling the forward moving, reverse moving, and/or braking of the electric car. The commercially available motor controller controls the forward moving, reverse moving, and braking of the control target by using a manipulation tool installed at a transmitter used to manipulate the control target. In the commercially available motor controller, a manipulation state for moving a control target forward is referred to as a forward mode, a manipulation state for moving the control target in reverse is referred to as a reverse mode, and a manipulation state for braking the control target is referred to as a brake mode.
Specifically, the manipulation tool may be a rod-shaped stick lever or a gun-trigger-shaped lever, which can be manipulated in two directions from a neutral point. The manipulation tool returns to the neutral point automatically after being manipulated. One direction from the neutral point is allocated for a manipulation state (mode) such as a forward mode, and the other direction from the neutral point is allocated for another manipulation state such as a reverse mode. The neutral point is not allocated for any mode of the motor controller.
Although there is a motor controller having three modes as manipulation states, the motor controller allocates one direction of a manipulation tool for a forward mode and the other direction of the manipulation tool for one of a brake mode and a reverse mode.
Therefore, when the manipulation tool is moved in the other direction, several methods are practically used for selecting one of the brake mode and the reverse mode.
According to one of such practical methods, a changeover switch is used to select the brake mode or the reverse mode. Alternatively, in a motor controller not using a changeover switch, the mode allocation of a manipulation tool is changed, for example, from forward and brake modes to forward and reverse modes in response to an operator's predetermined manipulation of the manipulation tool.
Next, with reference to FIG. 5, an explanation will be given on a motor controller that changes manipulation mode when a manipulation tool is manipulated in a predetermined manner. FIG. 5 illustrates an exemplary conventional motor controller. A control-data signal is output according to the manipulation amount of a manipulation tool (not shown) installed in a transmitter (not shown) and is transmitted to a receiver 11 where the control-data signal is demodulated. Then, based on the demodulated signal output from the receiver 11, a motor controller 30 controls the operation of a motor 12 installed in a control target, such as the rotation direction and rotation speed of the motor 12.
Specifically, when a rotation direction of the motor 12 for moving the control target forward is referred to as a forward direction and a rotation direction of the motor 12 for moving the control target in reverse is referred to as a reverse direction, the operation of the motor 12 is controlled as follows. When the manipulation tool is manipulated in one direction, the motor 12 is rotated in the forward direction, and when the manipulation tool is manipulated in the other direction, the motor 12 is braked or rotated in the reverse direction. At this time, the speed or brake power of the motor 12 is increased or decreased according to the manipulation amount of the manipulation tool so that the forward moving, reverse moving, or braking of the control target can be controlled. Here, the braking of the control target means a braking action against a forward movement of the control target.
Next, the structure of the motor controller 30 will be explained in detail. A signal demodulated by the receiver 11 is input to a control unit 31 through a buffer circuit 1. The control unit 31 converts the demodulated signal to a control signal by referring to a set value stored in a memory unit 32 and outputs the control signal to a drive circuit 3. The drive circuit 3 outputs a driving signal to the motor 12 based on the control signal for controlling the operation of the motor 12.
A current detecting circuit 4 detects the current flowing through the drive circuit 3 and transmits a detected current value to the control unit 31. The control unit 31 compares a maximum current value stored in the memory unit 32 with the current value received from the current detecting circuit 4 so as to control the current flowing through the drive circuit 3.
A manipulation unit 6 is a switch used to change the control state of the motor controller 30 for controlling the motor 12, and the setup state of the memory unit 32 for changing the set value stored in the memory unit 32.
In the motor controller 30, set values stored in the memory unit 32 can be changed. Examples of changeable set values include a maximum current value of the drive circuit 3 and data about a high point of the manipulation tool at which the output power of the motor 12 is maximal. Changing of a set value is carried out by reading a set value from an external device 34 through a serial communication circuit 33 and storing the read set value in the memory unit 32 through the control unit 31 (refer to Patent Document 1).
An explanation will now be given on changing of a mode indicating a manipulation state. Generally, in a motor controller, manipulation of a manipulation tool in one direction is allocated for a forward mode, and manipulation of the manipulation tool in the other direction is allocated for a brake mode. When the manipulation tool is returned to a neutral point after the manipulation tool is manipulated in the other direction to brake a control target, a control unit changes the mode to allocate the manipulation of the manipulation tool in the other direction to a reverse mode.
Furthermore, in the motor controller, if the manipulation tool is manipulated in one direction from the neutral point after the other direction is allocated for the reverse mode, the control unit changes the mode to allocate the other direction of the manipulation tool for the brake mode.
However, in the motor controller, when the manipulation tool is returned to the neutral point after the control target is braked, the mode is changed from the brake mode to the reverse mode. Therefore, an operator cannot brake the control target finely. That is, fine brake manipulation (so-called pumping brake manipulation) cannot be done for intermittently braking the control target.
Furthermore, mode changing can be performed although an operator does not intend. In this case, the control target may behave abnormally, and thus, the control target may be broken.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. H6-312065